[HN Gopher] Inverters with constant full load capability for ele...
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Inverters with constant full load capability for electric drives
Author : cl3misch
Score : 63 points
Date : 2024-04-19 07:05 UTC (1 days ago)
(HTM) web link (www.izm.fraunhofer.de)
(TXT) w3m dump (www.izm.fraunhofer.de)
| _Microft wrote:
| If you are wondering about the project name "Dauerpower":
| "Dauer-"/"andauernd" means permanent/permanently/continous and
| and - equally important - it rhymes with power ("d-ower").
|
| Here [0] is a longer article by Fraunhofer on silicon carbide
| power electronics. Depending on how much you want to know, there
| are Wikipedia articles on a number of terms used in it (SiC,
| MOSFET, wire-bonding, micro-via, parasitic inductance, IGBT, ...;
| there is also an explanation of "PCB embedding" on the Fraunhofer
| website [1]).
|
| [0] https://blog.izm.fraunhofer.de/silicon-carbide-for-power-
| ele...
|
| [1]
| https://www.izm.fraunhofer.de/en/abteilungen/system_integrat...
| algo_trader wrote:
| What is the cheapest/simplest configuration for an agricultural
| PV-to-always-on-e-motor (1MW)?
|
| We can serialize the PVs to get 1000v? And then feed that
| directly to a (suitable) drive without an inverter? Possibly
| even a DC motor?
|
| This cuts out half the components compared to an EV drive
| train, since we have much simpler cooling/packaging/response
| demand?
| WJW wrote:
| What is even the the point of that? An always-on (presumably
| only on during daytime?) 1 MW motor with enough solar panels
| to power them and something that actually requires a full
| megawatt would be pricy enough that the cost of an inverter
| would not be all that large percentage wise. Especially since
| you almost certainly would want to have some sort of
| controller for the motor anyway, which would need the same
| type of electronics as an inverter would need.
| rdl wrote:
| I would assume a huge pump of some kind.
| jandrese wrote:
| Probably an irrigation pump that needs to move water
| uphill. Water is heavy.
| AYBABTME wrote:
| What sort of agricultural PV-to-always-on-e-motor object
| would require 1MW continuously? That's a lot of power for
| agriculture purposes.
| namibj wrote:
| Most modern panels seem to be rated for a system voltage of
| up to 1500V; i.e., you're allows to connect enough in series
| to get up to but not beyond, as long as your MPPT can cope.
|
| And yeah, 1kV target is practical, you could run a triple
| half bridge inverter from that into a motor with enough stray
| inductance to smooth the PWM into pure sine, yeah. It can do
| the MPPT task at the same time, btw.
| shkkmo wrote:
| If your feeding DC from PV to a motor without an inverter, it
| will be a DC.
|
| If you hook a brushless motor straight to PV panels, the
| speed the motor runs at vary throughout the day as the
| volatage output of the panels waxes and wanes. You'll need to
| make sure that it the motor has sufficient cooling to not
| damage itself when running at full power on the hottest
| sunniest day.
|
| Generally, almost every type of PV or DC electric motor setup
| has a one or more systems that manage volatage, either in the
| form of a charge controller the outputs a constant(ish)
| voltage given the varying input voltages provided by the PV,
| or an ESC that outputs varying voltages to the motor to
| change it's rate of speed.
| quailfarmer wrote:
| To get good efficiency from a solar panel you must
| continuously track the "Maximum power point" (MPPT). You
| would never want to run a motor directly off the solar, you
| want a power converter to maximize efficiency.
| yobbo wrote:
| Closest English cognate is probably "enduring".
| jjtheblunt wrote:
| in both cases, German and English, through Latin borrowing
|
| https://en.wiktionary.org/wiki/dauern
| tgtweak wrote:
| Cool project, I like the incorporation of 3d-printed copper heat
| syncs with integrated coopant channels to the specific components
| so that they can control coolant distribution more accurately.
| That has applicability in many other areas.
|
| As battery tech gets better and energy densities increase, these
| improvements in inverter tech are critical to keep up. This could
| also mean improved AC output in battery energy storage systems as
| wel.
| pfdietz wrote:
| Inverters are becoming a larger fraction of the cost of PV
| systems, so improvements in the technology are welcome there as
| well.
| CoastalCoder wrote:
| Which components in a modern house could run as, or more,
| efficiently if fed DC power?
|
| I'm guessing this includes:
|
| - Most electronic devices that require AC->DC power adapters.
| Including CPUs, GPUs, and everything powered by USB.
|
| - Electric stoves, ovens, and other simple electric heaters.
| realreality wrote:
| > Electric stoves, ovens, and other simple electric heaters.
|
| Not really. The current would be too high on low voltage DC.
| And high voltage DC is dangerous.
| user_7832 wrote:
| > And high voltage DC is dangerous.
|
| Is this also at 120V or 220V DC? Is it due to how the
| alternating current allows muscles to release? (Or was that
| just a myth?)
| wcunning wrote:
| It matters for switches and things releasing in a physical
| sense, so muscles may not come into it. Also, there are
| issues with high voltage DC contactors welding themselves
| closed in high demand EV situations because they were sized
| incorrectly or had poor control.
| user_7832 wrote:
| Thanks, dangerous in the sense of damaging
| equipment/starting a fire? (As opposed to say shocking
| someone)
|
| > Also, there are issues with high voltage DC contactors
| welding themselves closed in high demand EV situations
| because they were sized incorrectly or had poor control.
|
| Would this have have made a difference if it were AC? I
| think AC welding is also a thing.
| wcunning wrote:
| AC definitionally has zero voltage 60 times a second, so
| when you try to "disconnect" by breaking the switch, the
| flowing electricity doesn't hold the switch closed. It's
| why when you look at relays they're rated for 12VDC or
| 120VAC (that and the commonality of house voltage and
| automotive voltage). I think the true values are probably
| a little higher in each, but you'd find that relays
| _cannot_ break contact at 120VDC where they can at
| 120VAC.
| user_7832 wrote:
| Thank you! So it's the "stickiness" of DC causing these
| problems, eh? I wonder if there are applications where
| the DC could temporarily be converted to AC or turned
| into some kind of oscillating DC temporarily to use more
| hardware.
| 20after4 wrote:
| >So it's the "stickiness" of DC causing these problems,
| eh?
|
| Yes, but it's more than just sticky in the sense of
| welded-contacts. A DC Arc is a continuous plasma that is
| conductive. That means the arc continues even with a
| significant air gap. The arc stretches as contacts are
| separated and yet the arc continues. That means that
| fuses can burn out completely but still conduct. Breaker-
| switches can trip and then catch fire while they continue
| to conduct rather than safely interrupting the arc. So
| fuses, breakers and relays all need to be designed
| specifically for DC or significantly de-rated compared to
| their AC voltage and amperage ratings.
|
| > applications where the DC could temporarily be
| converted to AC
|
| Yes and that involves an inverter.
| lazide wrote:
| DC arcs don't self extinguish like AC ones do, because
| there is no zero-voltage crossing phase point. For a given
| voltage, it makes DC much harder on relays, and DC relays
| are more expensive and harder to produce.
|
| This is true even though AC peak voltage is quite a bit
| higher than the RMS AC voltage. 170V for '120V AC' for
| instance.
| user_7832 wrote:
| Thanks!
| user_7832 wrote:
| I'd imagine DC-DC conversion to be a bigger pain. Inc
| comparison is AC-AC is very easy, while you can use switched
| supplies and what not it can be noisy in an EMF/RF context. And
| low voltage DC (even something as "high" as 24V) can have
| massive sag/voltage drop off over 10-20m of wiring, similar to
| what the other commenter mentioned.
|
| (Technically I'm sure using for eg motors, DC-DC could be done
| with minimal EMF noise, but you might end up with audible noise
| and efficiency losses.)
| amluto wrote:
| Unless you're using a transformer, AC adds a complication:
| energy storage. A device that takes AC in, wants to have a
| high power factor draw's power that's proportional to V^2, so
| the _power_ is a sine wave at twice the input frequency. Most
| loads want power that doesn't have 100% ripple at 120 Hz, so
| the power supply somehow needs to store about a half-cycle
| worth of power to out the ripples. As a practical matter, you
| end up with two-stage power conversion, where the first stage
| is a "power factor corrected" conversion to a high
| intermediate voltage and the second stage converts to the
| final voltage.
|
| Similarly, for AC _output_ , you want that 100% ripple on the
| output but not on the input.
|
| Three-phase AC avoids this particular problem -- power factor
| 1.0 with >= 3 passes has constant total power. But even a
| three-phase-AC motor drive producing variable frequency
| three-phase output has an internal DC bus.
|
| As a practical matter, IMO all large residential loads except
| resistive heating either should be, or already are, either DC
| or variable frequency drives.
| ReptileMan wrote:
| - Electric stoves, ovens, and other simple electric heaters.
|
| Resistance heaters don't care at all about DC or AC. And with
| induction you actually have to make the current AC with
| frequency around 50khz so I don't think it will matter that
| much in the grand scheme of things if you start with AC or DC.
| namibj wrote:
| DC would even be cheaper, you could skip the PFC front-end.
| amluto wrote:
| You could surely build an induction heater that has high
| power factor without a PFC front end by modulating the
| output at 120Hz. The result might be a loudly buzzing pan,
| though.
| nabla9 wrote:
| Heaters don't care. Zero effect.
|
| High power ~300W AC/DC conversion is 90% efficient.
|
| Low power ~1W AC/DC conversion is typically 65% efficient, but
| the energy used is also very small.
| naasking wrote:
| Very small but arguably 10x-100x more numerous, so it's not
| negligible. Especially once you start accounting for the
| spread of LED lighting.
| nabla9 wrote:
| Not negligible, but small. Lighting is roughly 9 percent of
| home electricity usage, TV and Media Equipment: 4 percent.
| amluto wrote:
| LED lighting almost invariably wants constant current DC,
| so there's a conversion stage regardless. The only major
| sort-of exception is LED tape, which uses a constant
| voltage supply, but internally, and lossily, regulates
| current.
|
| A modern high-quality LED light bulb uses a little IC that
| controls a non-isolated switching converter. You can find
| excellent datasheets online.
| mindslight wrote:
| If we assume induction motors get replaced by ECM motors or 3
| phase induction motors with VFDs, then everything but aquarium
| pumps and hair clippers? /me ducks.
| crote wrote:
| Basically, nothing.
|
| The problem is voltage. USB needs 5V, CPUs/GPUs need 0.8V-1.4V
| (you feed them 12V, but that gets down-converted), plenty of
| other chips need 3.3V. You can't wire a home for 5V or even 12V
| DC because the losses would be unacceptably high.
|
| This means a full-home DC grid would need to run more like
| 100V-200V DC, so you need DC-DC conversion at every point of
| use. And efficiency-wise AC->DC or DC->DC don't differ much.
| They're both around 95% in ideal scenarios, or more like 80% in
| real-world use. It really isn't worth the effort.
| crmd wrote:
| > Following a simulation phase, the prototype is currently under
| construction and will ultimately undergo an extensive testing
| process at Porsche AG
| kwhitefoot wrote:
| What's the real application here? It surely can't be automotive,
| the amount of time spent at full load is minuscule at least in
| cars. My old Model S has a full load output of 250 kW but the
| typical load is less than 30 kW. Lower power cars spend a bit
| more time at a higher fraction of full load but still typically
| far less than 50%.
|
| Of course efficiency and cooling are important but EV drives are
| already quite efficient and rarely operate at full load so the
| improvement in practice will be small.
|
| Or is the mention of automotive use relevant only because Porsche
| is involved in testing?
| lazide wrote:
| 100% duty cycle capable means more durable and capable of
| industrial use, racing, aerospace, military.
|
| Think mining haul trucks, industrial process control, towing,
| semi trucks, race cars, electric helicopters, water pumps, etc.
|
| also, likely capable of 150% for short bursts (military power)
| p1mrx wrote:
| > also, likely capable of 150% for short bursts
|
| Existing inverters are already capable of 150% for short
| bursts, if you define 100% to be the constant full load
| capacity.
| ju-st wrote:
| The 'full load' designation may be a distraction as the
| research appears to be focused on improving the cooling in
| general which obviously enables the use of less efficient and
| cheaper electronics.
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